A disk array apparatus for storing a large amount of data comprises a multiplicity of disk storage devices and the like connected with each other and provides, for example, a storage area in accordance with RAID (Redundant Array of Independent Inexpensive Disks). Each of disk storage devices comprises, for example, a plurality of disk drives, such as hard disk drives. The plurality of disk drives are mounted side by side and attached onto an electric circuit board for connection, called a “backboard.” Because the disk drives generate heat while they are in use, the disk drives are conventionally cooled by feeding cooling air into the disk storage device. Specifically, the disk storage device is provided with a fan (for air blow or intake) for forced air cooling to supply cooling air to clearances between the disk drives. The cooling air that has removed heat from the disk drives is exhausted outside from an exhaust hole provided in the housing of the disk storage device, and thus the internal temperature is prevented from rising.
Another known method is a technique for carrying out cooling in which a flat plate-shaped heat pipe is attached to an electronic appliance to transport the heat of the electronic appliance to the outside of its housing through the heat pipe.
Conventionally, cooling of disk drives is carried out by forcibly supplying cooling air inside the housing, and therefore, it is necessary to have sufficient clearances between disk drives accommodated in the housing at a high density so as to form a flow path for the cooling air. As a result, the housing size of the disk storage device is likely to increase corresponding to the clearances allocated to the cooling air flow path, making it difficult to meet the market demands for size reduction.
In addition, in many cases, an opening for exhaust is formed in the backboard in order to exhaust the cooling air circulated through the clearances between disk drives to the outside of the disk storage device. The reason is that the cooling air can be relatively smoothly exhausted when an opening is formed in the backboard since the backboard is provided at the rear ends of the disk drives so as to lid the clearances between the disk drives. For this reason, in the case of cooling structure in which cooling air is supplied between the disk drives, a large number of openings are formed in the backboard according to the number of disk drives accommodated. The backboard is, however, not only for mechanically supporting the disk drives but its original purpose is to electrically connect the disk drives with each other. Specifically, the backboard has a wiring pattern formed thereon and connected to each of the disk-drives, and through the wiring pattern, such operations are performed that power is supplied to each of the disk drives and data are read/written. Accordingly, when a large number of openings are formed or a single opening having a large area is formed in the backboard, the wiring pattern must be formed so as to bypass such opening(s), forcing the wiring line length of the wiring pattern to be longer than is necessary. Moreover, the presence of such opening(s) restricts the area in which the wiring pattern can be formed, and therefore, the wiring pattern may be densely packed in a particular area. When a wiring line length is made longer than is necessary or the wiring pattern is densely packed extremely, adverse effects such as noise are likely to occur, reducing the electrical characteristics.